Effect

Generation I

Rest causes the user to fall asleep, restoring its HP to its maximum amount and replacing any existing non-volatile status condition. The user will then be asleep for two turns, waking up on the second. Rest will fail if the user has full HP.

A glitch causes the stat reductions associated with paralysis and burn to remain despite the fact that the Pokémon no longer has that status. If a Pokémon that has been badly poisoned by Toxic successfully uses Rest, it will be cured of poison, but Toxic's N parameter is not reset; if it then suffers burn, Leech Seed or poison damage, that damage will be calculated with the formula for bad poison, still being calculated as N * x, and the N value will still increase by 1 each time (however, if the Pokémon is poisoned with Toxic, the N value will be reset to 1).

In the Generation Icore series only, Rest will also fail if the difference between the user's maximum HP and current HP leaves a remainder of 255 when divided by 256 (such as 255 or 511).

Generation II

The user will now awaken from Rest three turns after it is used and can attack on the third. If Rest is used through Sleep Talk, it will restore the user's HP and reset the number of turns the user will remain asleep to two.

Any major status conditions the user is affected by will now be cured. Safeguard will not prevent usage of Rest, and the user of Safeguard will still sleep the full two turns.

Generations III to IV

Rest now fails if it is used via Sleep Talk, regardless of the user's HP.

If a Pokémon with the Early BirdAbility uses Rest, its Ability still applies and the Pokémon's turns asleep will be rounded down from three to one.

Rest will automatically fail if used by a Pokémon with Insomnia or Vital Spirit, as these Abilities prevent them from falling asleep. Rest will also fail when used while Uproar is in effect, except when the user has Soundproof.

Rest can be used as part of a Pokémon Contest combination, with the user gaining two extra appeal points if any of the moves Belly Drum, Charm or Yawn was used in the prior turn. It can also be used to start a combination, causing Sleep Talk and Snore's base appeal points to be doubled if used in the next turn.

In other games

Jigglypuff uses Rest as its down B attack in the Super Smash Bros. series. Its effect is vastly different than its Pokémon game counterpart, as rather than healing the player, it launches the opponent into the air and plants a damage-inflicting flower on their head (in Brawl and SSB4) or sets them on fire (in Melee and the original SSB). This is a close-range attack with the hitbox placed at the center of Jigglypuff's body; using it even right next to the target will fail. If the attack misses, Jigglypuff will fall asleep doing no damage and leaving itself open to attacks.

Trivia

Although Rest does not deal any damage in the normal games, in the Super Smash Bros. series, Jigglypuff's Rest attack unleashes an internal explosion that sends any opponent it touches flying, almost always ending in a KO.

According to Webster's friend in Johto, Rest is a contraction of Recover fast.